The present invention relates to measuring instruments, and more particularly to apparatus for determining the string tension of a tennis racquet after it has been strung.
The tension in the strings of a tennis racquet is an important factor in determining the accuracy and speed with which a player may stroke a tennis ball. Players take a great deal of care to insure that their racquets are strung with a proper material and that the material is properly tensioned to their personal specifications best suited to their individual style of play. There exists a number of devices which are well suited to initially string a racquet to the personal specifications of even the most demanding tennis player. However, the tension will often dissipate after a period of use or even during storage. The materials with which tennis racquets are strung are affected by changes in humidity and temperature. For instance, catgut and to a lesser extent even nylon stretch when exposed to high humidity or high temperature. In damp climates the tension can change significantly in the matter of a few hours. Most players rely merely on the feel of the racquet to determine whether the string tension has deteriorated to a point where the player must adjust his stroke or even have the racquet restrung. There is, therefore, the need for an inexpensive, accurate and portable apparatus for measuring the string tension in a tennis racquet.
In the past a number of devices have been provided to enable a player to measure the tension of a single string of a tennis racquet. Such devices are shown in U.S. Pat. No. 3,831,442 to Cummins and U.S. Pat. No. 3,384,225 to Burchett. These devices merely clip on to a single string of the tennis racquet and measure the tension in that string by deflecting it between cooperating surfaces of the measuring apparatus. Although these devices provide useful measurement of string tension, they have limited accuracy because they measure the tension of only one string. Furthermore, the individual string which is being measured and, in fact, the whole tennis racquet face is apt to move during a measurement and further limit the accuracy of these devices. It is also possible that a string whose tension is being measured by one of these devices could break thus requiring the complete restringing of the racquet.
There is a need for an inexpensive, accurate and completely portable device for measuring the string tension of a tennis racquet after it is strung without the disadvantages of the prior art devices.